1. Field of the Invention
The present invention relates to a light-emitting device including light-emitting elements such as LED elements or the like, more specifically to a light-emitting device with a planar light-emitting area.
2. Description of the Related Art
Conventionally, there is proposed a light-emitting device configured to acquire various light-emitting colors by a color mixing of light obtained from a combination of a light source and a phosphor plate excited by light emitted from the light source and capable of emitting light of color phase different from light-emitting color of the light source. In particular, a light-emitting device using a light-emitting diode element (hereinafter, referred to as LED element) as a light source has already been put into practical use as the next-generation illumination replaced by a fluorescent lamp, because the LED element has a low power consumption and a long service life, as a backlight for a crystal display, or a high brightness lamp reaching instantly to a high brightness, and further improvement in output, uniform light-emitting color and brightness in light-distribution are demanded.
FIG. 13 illustrates an example of a conventional light-emitting device.
The conventional light-emitting device 900 as schematically shown includes a circuit substrate 80, an LED element 10 mounted in a manner of flip-chip on an upper surface of the circuit substrate 80, a first light-reflection resin 40 covering the entirety of a side surface of the LED element 10, a phosphor plate 20 covering an upper surface of the LED element 10 and a part of an upper surface of the first light-reflection resin 40, and a second light-reflection resin 50 covering a side surface of the first light-reflection resin 40 and a side surface of the phosphor plate 20 (for reference, see JP2010-192629A). In the conventional light-emitting device, light leaked from the side surface of each of the LED element 10 and the phosphor plate 20 is reflected on the first light-reflection resin 40 and the second light-reflection resin 50 and returned into the LED element 10 and the phosphor plate 20.
On the other hand, there is known another conventional light-emitting device in which only the side surface of the LED element 10 is covered with the first light-reflection resin 40 and the side surface of the phosphor plate 20 is not covered (for reference, see JP2007-19096A).
In the conventional light-emitting device 900, by covering the side surface of the LED element with the first light-reflection resin 40 and the side surface of the phosphor plate 20 with the second light-reflection resin 50, light leaked from the side surfaces is reduced, as a result, it is possible to provide the light-emitting device 900 having a bright light-illumination surface.
However, as shown schematically in FIG. 14, for example, exit light Ph emitted right above from the LED element 10 emitting blue light is emitted as white light by color mixture of blue radiation light occurred by the fact that a distance passing the phosphor plate 20 is short and yellow radiation light occurred from a wave-conversion converted by, for example, YAG-system fluorescent particles dispersed in the phosphor plate 20. In contrast, exit light Py emitted obliquely above from the upper surface of the LED element 10 increases the number of impacting with the YAG-system fluorescent particles, thereby an amount converted into yellow increases and the exit light Py is yellowing, because the emitted light passes through the phosphor plate 20 throughout a longer distance than the distance of the exit light Ph passing through the phosphor plate 20 vertically. Therefore, as shown in FIG. 15, in a central portion on the irradiation surface of the light-emitting device 900, an adequate color mixture is achieved, thereby white color light 910 can be acquired. However, in a peripheral portion on the irradiation surface, the exit light appears to be a colored ring, and when YAG is used as a phosphor, yellow-ringed light caused by the YAG-system fluorescent particles, and therefore, a problem of a yellow ring 920 occurs.
In this way, in the conventional light-emitting device 900, by covering the side surface of the LED element 10 with the first light-reflection resin 40 and the side surface of the phosphor plate 20 with the second light-reflection resin 50, although the light leaked from these side surfaces can be reduced, a problem of the colored ring occurred by the light emitted obliquely above from the phosphor plate 20 is not resolved. In addition, there are minus factors such as the colored ring or leakage of light from the side surfaces of the LED element and so on, it is difficult to control or adjust the minus factors by optical systems such as lenses and so on.
In particular, as popularization of a light-emitting device using an LED element to an application field proceeds, a light-emitting device in which light leaked from a side surface of an LED element is reduced, uniform light-emitting color is acquired to inhibit the occurrence of a colored ring, and light can be efficiently controlled has been demanded. For example, in case of illumination when photographing, light distribution for the illumination and brightness according to a view angle of a photographing lens are required, and in case of a color photograph, uniform light-emitting color having no colored ring or variation in color is requested.